Cambridge, UK and Cambridge, Massachusetts – 18 September 2007 – Acambis plc (Acambis) (LSE: ACM) welcomes sanofi pasteur’s reported progress with a dengue vaccine candidate based on technology licensed from Acambis. Sanofi pasteur, the vaccines division of the sanofi-aventis Group, has announced positive results from Phase 2 trials and plans to start a Phase 3 trial programme in 2008.